Ultrafast and Ultralarge Lithium-Ion Storage Enabled by Fluorine-Nitrogen Co-Implanted Carbon Tubes.

As a holy grail in electrochemistry, both high-power and high-energy electrochemical energy storage system (EES) has always been a pursued dream. To simultaneously achieve the "both-high" EES, a rational design of structure and composition for storage materials with characteristics of battery-type and capacitor-type storage is crucial. Herein, fluorine-nitrogen co-implanted carbon tubes (FNCT) have been designed, in which plentiful active sites and expanded interlayer space have been created benefiting from the heteroatom engineering and the fluorine-nitrogen synergistic effect, thus the above two-type storage mechanism can get an optimal balance in the FNCT. The implanted fluorine heteroatoms can not only amplify interlayer spacing, but also induce the transformation of nitrogen configuration from pyrrole nitrogen to pyridine nitrogen, further promoting the activity of the carbon matrix. The extraordinary electrochemical performance as results can be witnessed for FNCT, which exhibit fast lithium-ion storage capability with a high energy density of 119.4 Wh kg-1 at an ultrahigh power density of 107.5 kW kg-1 .

An Active-Oxygen-Scavenging Oriented Cathode-Electrolyte-Interphase for Long-Life Lithium-Rich Cathode Materials.

Lithium-rich layered oxides with high energy density are promising cathode materials, thus having attracted a large number of researchers. However, the materials cannot be commercialized for application so far. The crucial problem is the releasing of lattice oxygen at high voltage and resulting consequence, such as decomposition of electrolyte, irreversible phase transition of crystal structure, capacity degradation, and voltage decay. Therefore, capturing active-oxygen and further constructing a cathode-electrolyte-interface (CEI) protective layer via the scavenging effects should be a fundamental step to solve these issues. Herein, ß-carotene with antioxidant properties is used as a scavenging molecule to achieve this goal. The control of active oxygen species effectively alleviates the decomposition of carbonate electrolyte under high voltage. The introduction of ß-carotene additives can also be adjusted in situ to generate a customized CEI film, which is a double-layer structure with external organic components and internal inorganic components. Moreover, the ß-carotene-containing electrolyte system exhibits better thermal stability. Benefited from these, Lithium-rich cathode of ß-carotene-containing electrolyte shows outstanding long-life cycle stability, with 93.4% capacity retention rate after 200 cycles at 1 C; this electrochemical stability is superior to other electrolyte additive systems reported at present.

Regulating Lithium Plating/Stripping Behavior by a Composite Polymer Electrolyte Endowed with Designated Ion Channels.

The urgent demand for high energy and safety storage devices is pushing the development of lithium metal batteries. However, unstable solid electrolyte interface (SEI) formation and uncontrollable lithium dendrite growth are still huge challenges for the practical use of lithium metal batteries. Herein, a composite polymer electrolyte (CPE) endowed with designated ion channels is fabricated by constructing nanoscale Uio66-NH2 layer, which has uniformly distributed pore structure to regulate reversible Li plating/stripping in lithium metal batteries. The regular channels within the Uio66-NH2 layer work as an ion sieve to restrict larger TFSI- anions inside its channels and extract Li+ across selectively, which result in a high Li-ion transference number ( t Li + ${t_{{\rm{L}}{{\rm{i}}^{\bm{ + }}}}}$ ) of 0.6. Moreover, CPE provides high ion conductivity (0.245 mS cm-1 at room temperature) and expanded oxidation window (5.1 V) and forms a stable SEI layer. As a result, the assembled lithium metal batteries with CPE exhibit outstanding cyclic stability and capacity retention. The Li/CPE/Li symmetric cell continues plating/stripping over 500 h without short-circuiting. The Li/CPE/LFP cell delivers a reversible capacity of 149.3 mAh g-1 with a capacity retention of 99% after 100 cycles.

High-Performance Lithium-Oxygen Batteries Using a Urea-Based Electrolyte with Kinetically Favorable One-Electron Li2 O2 Oxidation Pathways.

Glymes are the most widely used electrolyte solvents in lithium-oxygen batteries (LOBs) due to their relatively high stability. However, their associated LOBs have long been plagued by large charge overpotential, which is closely related to the sluggish two-electron Li2 O2 oxidation mechanism. Here, we report a new electrolyte solvent-1,1,3,3-tetramethylurea (TMU) for LOBs with high performance and an alternative mechanism, where a kinetically favorable one-electron Li2 O2 oxidation pathway can happen in the urea electrolyte system, thus leading to a much lower charge overpotential (≈0.51 V) compared to the tetraglyme-based LOBs (≈1.27 V). Besides, TMU also exhibits good stability since it does not contain any α-hydrogen atoms that are vulnerable to be attacked by superoxide species, thus suppressing the hydrogen abstraction side reactions. Consequently, the TMU-based LOBs can stably work for more than 135 cycles, which is four times that of the tetraglyme-based LOBs (≈28 cycles).

A weakly coordinating-intervention strategy for modulating Na+ solvation sheathes and constructing robust interphase in sodium-metal batteries.

Constructing powerful anode/cathode interphases by modulate ion solvation structure is the principle of electrolyte design. However, the methodological and theoretical design principles of electrolyte/solvation structure and their effect on electrochemical performance are still vague. Here, we propose a cationic weakly coordinating-intervention strategy for modulating the Na+ solvation sheathes and constructing robust anode/cathode interphases in sodium-metal batteries. Unlike the local highly concentrated electrolytes, 1,2-difluorobenzene can weakly coordinate with Na+ thus transforming the solvation structure into Na+-anion-incorporated structures and strengthening anode/cathode interphases formation by combining with salt decomposition. Furthermore, the correlations between the electrode interface properties and solvation structure are revealed, which can be tuned by the weakly coordination. Ultimately, the modulated electrolyte achieves 97.5% Coulombic efficiency for 600 cycles in Na‖Cu cells at 1 mA cm-2 and a beneficial lifetime (2500 h) in Na‖Na cells. Meanwhile, Na‖PB cells have achieved long-term operation at 4.8 V, along with operation at wide temperatures.

Constructing an Interlaced Catalytic Surface via Fluorine-Doped Bimetallic Oxides for Oxygen Electrode Processes in Li-O2 Batteries.

Lithium-oxygen (Li-O2) batteries, renowned for their high theoretical energy density, have garnered significant interest as prime candidates for future electric device development. However, their actual capacity is often unsatisfactory due to the passivation of active sites by solid-phase discharge products. Optimizing the growth and storage of these products is a crucial step in advancing Li-O2 batteries. Here, a fluorine-doped bimetallic cobalt-nickel oxide (CoNiO2- xFx/CC) with an interlaced catalytic surface (ICS) and a corncob-like structure is proposed as an oxygen electrode. Unlike conventional oxide electrodes with a "single adsorption catalytic mechanism," the ICS of CoNiO2- xFx/CC offers a "competitive adsorption catalytic mechanism," where oxygen sites facilitate oxygen conversion while fluorine sites contribute to the growth of Li2O2. This results in a change in Li2O2 morphology from a surface film to toroidal particles, effectively preventing the burial of active sites. Additionally, the unique open architecture aids in the capture and release of oxygen and the formation of well-contacted Li2O2/electrode interfaces, which benefits the complete decomposition of Li2O2 products. Consequently, the Li-O2 battery with a CoNiO2- xFx/CC cathode demonstrates a high specific capacity of up to 30923 mAh g-1 and a lifespan exceeding 580 cycles, surpassing most reported metal oxide-based cathodes.

A Novel Metal-Organic-Framework-Based Composite Solid Electrolyte for Lithium Metal Batteries.

Solid-state lithium metal batteries are hindered from practical applications by insufficient room-temperature ionic conductivity and poor electrode/electrolyte interfaces. Herein, we designed and synthesized a high ionic conductivity metal-organic-framework-based composite solid electrolyte (MCSE) with the synergy of high DN value ligands from Uio66-NH2 and succinonitrile (SN). XPS and FTIR reveal that the amino group (-NH2) of Uio66-NH2 and the cyano group (-C≡N) of SN have a stronger solvated coordination with Li+, which can promote the dissociation of crystalline LiTFSI, achieving an ionic conductivity of 9.23 × 10-5 S cm-1 at RT. Afterward, a flexible polymer electrolyte membrane (FPEM) with admirable ionic conductivity (1.56 × 10-4 S cm-1 at RT) and excellent electrode/electrolyte interfaces (86.2 Ω for the Li|20% FPEM|Li cell and 303.1 Ω for the LiFePO4|20% FPEM|Li cell) was successfully obtained after compounding the MCSE with polyethylene oxide (PEO). Moreover, a stable solid electrolyte layer (SEI) was formed in situ on the surface of the lithium metal, which enables the Li|20% FPEM|Li cell to exhibit remarkable cycling stability (1000 h at a current density of 0.05 mA cm-2). At the same time, the assembled LiFePO4|20% FPEM|Li cell offers a discharge-specific capacity of 155 mAh g-1 at 0.1 C and a columbic efficiency of 99.5% after 200 cycles. This flexible polymer electrolyte provides a possibility for operating long lifespan solid-state electrochemical energy storage systems at RT.

An Organic Redox Mediator with a Defense-Donor for Lithium Anode in Lithium-Oxygen Batteries.

Lithium-oxygen batteries (LOBs) suffer from large charge overpotential and unstable Li metal interface, which can be attributed to the inefficient charge transport at the insulating Li2 O2 /cathode interface and the severe oxygen corrosion issue on the Li anode surface. The use of soluble redox mediators (RMs) can effectively enhance the charge transport between Li2 O2 and cathode, thus greatly reducing the charge overpotential. However, oxidized RMs will also shuttle to the anode side and react with the Li metal, which not only results in the loss of both the RMs and the electrical energy efficiency but also exacerbates the Li anode corrosion. Herein, an organic compound-acetylthiocholine iodide (ATCI), in which a big cation group is contained, is proposed as a defense-donor RM for lithium anode in LOBs to simultaneously address the above issues. During charge, it can accelerate the oxidation kinetics of Li2 O2 via its iodide anion redox couple (I- /I3 - ). Meanwhile, its cation segment (ATC+ ) can move to the anode surface via electric attraction and in situ forms a protective interfacial layer, which prevents the Li anode from the attack of oxidized RM and oxygen species. Consequently, the ATCI-containing LOBs can achieve both a low charge potential (≈3.49 V) and a long cycle life (≈190 cycles).